Motor vehicle crashes are the leading cause of fatal injury of children under age five in the U.S. In 1985, motor vehicle crases killed 1,195 children under age five and, in 1986, moving motor vehicles injured 246,000 children under age five in the U.S.
Experts estimate that 66 to 90 percent of injuries and deaths could be prevented if child passengers were properly restrained in car safety seats (CSS's). In essentially all CSS systems, the seat portion of the device is held to the vehicle seat using at least a vehicle lap safety belt. Both the ends of the vehicle safety belt and the ends of the CSS harness straps must be connected during use for the CSS to function correctly. These connections are typically made by buckle assemblies that are similar in design. They comprise a perforated or notched latch plate (tongue) that is inserted into the buckle. Stop means (typically an indent or tang) on a latch member inside the buckle interact with the tongue to prevent its removal from the buckle prior to release by the buckle user.
Research funded by the National Highway Traffic Safety Administration (NHTSA) has shown that unauthorized release of safety belt and CSS harness buckles by young children can reduce the effectiveness of these child restraints to "close to zero." A survey of CSS users presented in the report referenced above found that 36 percent reported that their child had released a safety belt buckle at an inappropriate time and 21 percent had released a CSS harness buckle at an inappropriate time. There is interest in improving conventional safety belt buckles by adding child-resistant features to prevent unauthorized release of these buckles by young children. For the purposes of this disclosure, the term "safety belt buckle" includes the buckles on vehicle safety belts (also called seat belts), those that hold the ends of CSS harnesses together and those that secure the ends of CSS harnesses or CSS harness shields to CSS frames.
Prior art devices for adding child-resistance to safety belt buckles have used two basic approaches to achieve this end. One approach is to enclose the buckle in a child-resistant housing. This approach is more appropriate for after-market devices that would be used to retrofit conventional buckles.
A second approach is to add integral child-resistant features to conventional buckle designs. Prior art devices to add integral child-resistant features to buckles have comprised movable members mounted on the buckle body for preventing movement of the latch member to a position that releases the buckle tongue, hence providing a measure of child resistance. Because buckle body components are present only on the base (and possibly the sides) of a free-standing buckle, the child-resistant feature(s) must also be attached to the base (or sides) of the buckle. In that safety belts and buckles should be worn snug against user's body, child-resistant features located on the base (or sides) of a buckle can be difficult to use. For this reason, buckles having child-resistant features attached to the top cover of the buckle and to the push button are of interest. Such buckle designs would be less likely to discourage safety belt and CSS use because inconvenient-to-operate child-resistant features are not added to these important safety products.